Draft-regulator for boiler-furnaces.



A. s. MANN.

DRAFT REGULATOR FOR BOILER FURNACES.

APPLICATION FILED OCT. 5, 1 90 7 I Patented beb. 20, 1919 2 SH EETS-SH [E I I l g- I 5'1 13 i I L 2 w 5 \L 0 0 o a o o o o o o o o o o o 5 E i I re m p:

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A. S. MANN.

DRAFT REGULATOR FOR BOILER FURNACES.

APPLICATION FILED OCT. 5. I907.

Patented Feb. 25, 1919.

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Ni i an ARTHUR S. MANN, F SCHENECTADY, NEW YORK, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A. CORPORATION OF NEW YORK.

DRAFT-REGULATOR. FOR BOILER-FURNACES.

Specification of Letters Patent.

Patented Feb. 25, 1919.

Application filed October 5, 1907. Serial No. 395,988.

To all whom it may concern:

Be it known that I, ARTHUR S. MANN, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Draft-Regulators for Boiler-Furnaces, of which the following is a specification.

This invention relates to devices for regulating the supply of air to furnace fires especially in connection with steam boilers. It is desirable to maintainin the fire box a pressure of the roducts of combustion just equal to that of the atmosphere because an excessive pressure on the one hand would cause an escape of gases into the furnaceroom, while, on the: other hand, a Vacuum would cause an inrush of cold air through every crevice, cooling down the fire, diluting the hot gases, and .:carrying an excess of heat up the chimney. Moreover, when the fire box pressure balances that of the atmosphere the heated products of combustion are held in contact with the heating surface of the boiler for" a longer period of time, owing to the lessening of dilution which decreases the velocity so that they exert a better heatingefl'ect. This system of firing is known as the balanced draft, and the object of my invention is .to provlde a simple and etlicient apparatus for accomplishing this result. The invention comprises a movable abutment responsive to variations in pressure in the fire box, a damper in the smoke stack for throttling the suction therein, and operative connections, preferably electrical, between said abutment and damper, whereby the latter will be moved toward the open position upon the occurrence of an excess of pressure above normal in the fire box, and toward the closed position upon a drop of such pressure below normal. The invention is especially designed for use with boilers having a forced draft, but is applicable to those having a natural draft.

In the accompanying drawings, Figure 1 is a sideelevation of a steam boiler and sure-responsive device; Fig. 4 is atop plan view of the same; Fig. 5 is an end view of the reversing switch and Fig. 6 shows the.

The boiler 1 is mounted on a furnace 2,

which'has a smoke-stack 3. In one wall of the fire-box, at some convenient point above the grate, is inserted a pipe 4, terminating outside the furnace in an upwardly curved elbow 5. I prefer to make the elbow separate from the pipe and cast it integral with a lid 6 which is hinged at its upper end to a frame 7 on the outer end of the pipe 4.

At the upper. end of the elbow 5 is located a movable abutment, preferably a bell 8 covering the end of said elbow and dipping into an annular water seal concentric therewith. Supported by the elbow are two arms 9 10 the former serving as a fulcrum for a lever 11, one end of which is ivotally attached to the bell, preferably by knife edges, as shown. The other arm of the lever has an gdljusta'ble counterweight 12 to balance the It will be evident that any variation in the pneumatic pressure in the fire-box above or below the atmospheric pressure in the furnace room will cause a movement of the bell up or down respectively. These movements are utilized to change the position of a damper 13 ,in the smoke-stack, in,order to increase or decrease the suction in said stack and thus compensate for the abnormal conditions in the fire box and restore them to normal. Any suitable motor may be employed to operate the damper. I prefer to use an electric motor, causing the bell to control a reversing switch for .runni-n'g the motor in one direction or the other as may be necessary.

The motor 14 may be conveniently supported on a shelf 15 bolted to the wall of the furnace. On the motor shaft is a bevel pinion 16 which meshes with a bevel gear 17 1 attached to a nut 18 which is rotatably mounted in a frame 19. A screw 20 meshes with said nut and said screw is continued as a rod 21 to a point where it can be operatively connected with the lever 22 which actuates the damper. The motor can rotate the nut one way or the other and thus move the rod up or down to open or close the damper. Fig. 2 shows one form of reversing switch for the motor. The lever 11 is connected with the negative main 23 of a supply circuit, and plays between two contacts 24 25 each of which is connected with positive main 26. In series with each contact 24 25 are two electromagnets 27 28, which control, respectively, the circuits of the motor armature 29 and field winding 30, in a manner which is clearly shown in the diagram.

The operation of the device is as follows: So long as the pneumatic pressure in the fire box balances that of the external atmosphere, the bell "8 will remain stationary, or practically so, and the lever 11 will stand midway between the two contacts 24 25. But if the fire box pressure rises or falls, the bell lifts or drops and the lever closes upon the contact 24 or 25, energizing the corresponding pair of electromagnets and closing the motor circuit. If, for instance the bell rises and the contact 24: is the active one, the direction of current through the armature 29 is such that the motor rotates the nut 18 left-handedly, pushing up the rod 21 and opening the damper 13 to give a greater draft in the stack and thus reduce the pressure in the firebox. The opposite effect is produced if the fire box pressure falls below normal. With some kinds of fuel it may be desirable to ad just the counterweight to keep the inside pressure a trifle below atmospheric in order to avoid all possibility of gas blowing out when the furnace door is opened. The regulation is very delicate, since the apparatus responds to a variation in pressure amounting to only a small fraction of an ounce. The advantages of a balanced draft are thus secured in the highest degree.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. The combination with a furnace having a fire-box and a draft check, of a bellfloat responsive to variations in pneumatic pressure in said fire-box, a motor for operating said draft check, and controlling means for said motor operated by said bell float.

2. The combination with a furnace having a fire-box and a draft check, of a bellfioat in direct communication with the interior of said fire-box, a reversing switch controlled by said bell float, and a motor controlled by said reversing switch and operatively engaging said draft check.

3. The combination Witha furnace havindirect communication with the interior of said fire-box, an electric motor controlled,

by the movements of said bell-float, a thread?- ed rod connected to said draft check, a swivthe combination with a furnace of a container, a member pivoted therein and normally maintained in a substantially horizontal position, an adjustable counterbalance for said member, a damper operatively connected with said member and controlling discharge of gases from said furnace, said member having on one side thereof a constant pressure and said member being acted upon on the other side thereof by the pressure of the furnace gases.

7. In a device of the character described, the combination with a furnace of a container, a member pivoted therein and normally maintained in a horizontal position,

a counter-balance for said member, means for varying the effective weight of said counterbalance, and a damper controlling discharge of gases, from said furnace and to which said member is operatively connected, said member being acted upon in one direction by a constant pressure and in the opposite direction by the pressure of the furnace gases.

8. In a device of the character described, the combination with a furnace having a combustion chamber, of a container communicating therewith, a member pivoted n said container and normally maintained in substantially a horizontal position, an adjustable counterbalance for said member, a relay mechanism actuated by said member, a motor controlled by said relay mechanism,

and a damper controlled by said motor and I controlling discharge of gases from said furnace, said member being acted upon n one direction by a constant pressure and in the opposite direction by the pressure of the furnace gases.

9. In a device of the character described, the combination with a furnace having a combustion chamber, of a container having an open side, a conduit communicating with said chamber and said container, a member I pivoted in said container and forming a movable closure for said open side, an adjustable counterweight adapted to maintain said member normally in substantially a horizontal plane, a damper for controlling the combination with a furnace having a combustlon chamber thereln, and means for automatically regulating the draft for combustion, said means comprisinga container having an open side and. communicating with said combustion chamber, a member pivoted in said container adapted to close said open side, an adjustable counterbalance for said member, a relay mechanism actuated by said member, a motor actuated by said relay mechanism, and a damper controlled by said motor and controlling dischargev of gases from said furnace, said member being acted upon in one direction by constant pressure and in the opposite direction by the pressure of the furnace gases.

11. In a device of the character described, the combination with a furnace having a combustion chamber and means for controlling the draft for combustion, said means consisting of a fluid container communicating with said combustion chamber, a member pivoted in said container and having depending sides extending into the fluid therein, an adjustable counterbalance for said member, the latter being maintained normally in substantially a horizontal position, and a damper operatively connected with said member and controlling discharge of gases from said furnace.

In Witness whereof, I have hereunto set my hand this 4th day'of October, 1907.

ARTHUR s. MANN. 

